Iridescent foil



March 26, 1940. c. F. SCHMIDT, JR., Er Al. 2,195,190

IRIDES CENT F0 IL Filed Dec. l2, 1938 Patented Mar. 26, 1940 UNITEDSTATES PATENT OFFICE IRIDESCENT FOIL Application December 12, 1938,Serial No. 245,316

13 Claims.

This invention relates to a composite foil.

Our invention herein disclosed bears an underlying relation to thatdisclosed in our co-pending application Serial No. 705,379, led January5, 1934. Whereas, however, our co-pending application deals primarilywith the production of a coated metallic foil, such as aluminum foil,which, as coated, is so resistant to chemical action, and has otherqualities in such sort, that it is suitable for use on lining elementsin container caps, this invention, is directed additionally to theproduction of a coated foil of novel and striking ornamental apperance.

In our co-pending application, above-noted, the metallic foil hasapplied thereto a coating material which, as heat treated, is highlyresistant to acids and alkalies, is not tacky or thermoplastic, isodorless and tasteless, and in Which the coating is so elastic, and thecoating and metallic base so bonded to each other, that they are ineffect a single material. These qualities are of primary importance infullling the purpose to which that foil is put. Incidentally, the foilas so made has a bright golden color.

In the composite foil of our present invention, we do not disregard theprimary qualities of rm bonded adhesion between the metallic base andthe non-metallic lm thereon, nor the elasticity of the film component ofthe coated foil. It is also desirable that the iilm of our ornamentalfoil should not be thermoplastic; and also that, for some purposes, itbe resistant to acids and alkalies.

While in our co-pending application the physical qualities of the coatedfoil are the chief desideratum, this invention relates to a metallic'foil which is of striking novel ornamental appearance without unduesacrice of the physical qualities of our coated foil above identiiied.By utilizing fundamentally the formulae and proredure as disclosed inour co-pending application, we have succeeded in producing a coatedmetallic foil which presents on its coated side an iridescent effect.This iridescence is obtained by varying the procedure disclosed in ourcopending application.

We shall rst describe, briefly and generally our preferred procedure inproducing an iridescent foil. The accompanying drawing shows,

diagrammatically, exemplary apparatus for producing our iridescent,composite foil. At an end, or ends, of an elongate heating furnace I,there are mounted two reels 2 and 3, upon one of Which is a roll of sometough and coherent foil which is to be treated, such as aluminum foil. Areceiving reel 3 for the treated foil takes the foil as it comes fromthe furnace. The foil is carried over guiding rolls 4 and 5 into thefurnace, the free end of the foil being connected with the collectorreel 3. In passage of the strip of foil to the heated region of thefurnace, one face thereof is contacted by an applicator roll 6, whichdips into a trough 'l of coating liquid. Desirably, means such aselectric heaters 8 are provided for subjecting the coated side of thefoil to moderate temperature for initially drying the coating materialin a region between the region at which the coating is applied and theentrance to the heated zone of the furnace through which the foil iscarried.

In the exemplary apparatus shown, the foil, as it enters and is carriedthrough the furnace, passes over a number of small diameter rolls 9. Atthe delivery end of the furnace, the foil is taken up by a pair of rollsI0 and Il. This pair of rolls is positively driven, and controls therate at which the foil is carried through the furnace. The collectingreel 3 is driven through a slipclutch l2, so that its progressivelyincreased diameter, as the foil collects on it, does not increase thespeed at which the foil travels through the furnace.

The elements which are positively driven are thus the propelling rollsl0 and Il, and the applicator roll 6. These rolls are in suitable mannerdrivable at variable speed; as the speed of the applicator roll 6controls the thickness of the coating applied to the foil, and the speedof the propelling rolls is a factor of primary importance in determiningthe time period of heat treatment to which the foil is subjected.

It should be explained that the length of heating zone in the furnace,and more particularly the length of the high temperature zone in thefurnace, plays a part in determining the time period of heat treatment.Thus if the furnace be 20 feet in length, there is only a portion ofsuch length in which the temperature to which the foil is subjectedapproximates the maximum. Assuming that the length of such hightemperature zone is ve feet, it is such length that is to be consideredin determining the time period of heat treatment of the foil.

In conducting a coating treatment of suitable metallic foil, such asaluminum foil, the coating applied by applicator roll 6 is initially setto the foil by the electric heating elements 8, and is fully set to thefoil in the 10W temperature zone at the entering end of the furnace. Itis, of course, highly desirable that the solvent thinner,

or thinners, comprised in the coating composition be thus driven 01Tbefore the coated foil encounters the high temperature at which heatconversion of the film is effected. Also it is of importance so quicklyto set the film on the metallic base that the film is smooth, anduninterrupted.

The coating which We prefer to use comprises coumarone resin; a resinhaving heat-curing properties, such as the phenolic resins; linseed oil;and China-Wood oil. The composition of the coating used is, however,susceptible of considerable variation, since the production of aniridescent foil depends largely upon temperature and duration of heattreatment, and also upon the thickness with which the coatingcomposition is applied to the foil. Taking constituents, such as thosenoted above, they are worked up into a relatively thin, flowable coatingcomposition by the addition of suitable solvent thinners, such as amixture of hi-ash naphtha and water-white kerosene. Pine oil, or itsequivalent, may be added to prevent possible separation in the thinnedcoating liquid. Other ingredients may desirably be added, such, forexample, as ozocerite Wax, to provide an unwettable surface; and a smallquantity of a surface-drying material, positively to prevent finaltackiness, such as manganese acetate, manganese oxide, cobalt acetate,cobalt resinate, or cobalt naphthanate.

It may be stated generally that there are four factors serving toproduce our iridescent, cornposite foil; namely, a suitable coatingcomposition, the thickness of the coating composition as applied to thefoil, the temperatures at which heat treatment of the coated foil iseffected, and the duration of the period through which the metallic baseand applied lm is subjected to heat treatment.

It may initially be explained that the thickness of the coating appliedto the metallic base, and the consequent thickness of lm thereon,depends in turn on two factors. One such factor is the quantity ofsolvent thinner with respect to the other ingredients in the coatingcomposition used, and the other is the quantity of coating compositionapplied to each unit area of the base.

As to the material used, we have successfully produced iridescent foilutilizing the base formulae given in our co-pending applicationA SerialNo. 705,379, with suitable thinners, and desirably with the otheringredients of the coatin-g composition there disclosed.

One formula which we have utilized for the production of iridescent foilis as follows:

Per cent Linseed oil 52.2 China-wood oil 11.2 "AmberoP No. F7 16.8Coumarone resin 16.8

Another typical formula which we have successfully employed is asfollows:

Per cent Linseed oil 55 China-wood oil 11 Amberol ST13'7 11 Coumaroneresin 23 The Amberol ST137 resin is known as a 100% heat-curing resin,and we have successfully replaced it in the formula by other phenolicresins generally understood to be heat-curing, such as Bakelite No.1329, Bakelite No. 3360, Beckacite No. 1001, and Durex No. 500.

We mayuse indene resins,instead of coumarone resin, and it will beunderstood that many cornmercial Coumarone resins, which can besuccessfully used, consist of mixtures of Coumarone and indene polymers.Moreover, synthetic resins having the general qualities of neutrality,adhesion, and inertness to acids and alkalies, possessed by coumarone,are to be regarded as equivalents of Coumarone. As examples ofequivalent resins which we have successfully substituted in likeproportion for Coumarone, we refer to synthetic petroleum resins, suchas Pur-o-resin, polymers of dihydronaphthalene, such as DuPontRH-35, andpolymers of cyclopentadiene and other cyclic dienes, such as Nuba Wehave also successfully used substituted and other modifiedcoumarone-indene resins.

The Pur-o-resin referred to above is manufactured by the Pure OilCompany, and is designated by them as P-198. This is a solid petroleumresin having a specific gravity of 1.023-1.029, a melting range of 190F., a minimum iodine number of 200, and a molecular weight ofapproximately 700. It consists of reduced hydrocarbon polymers producedby the polymerization of petroleum distillates obtained by vapor phasecracking. This may be produced, for example, as disclosed in theChittick Patent No. 1,891,079 of December 13, 1932.

The Du Pont RH-35 referred to above is manufactured by E. I. du Pont deNemours & Co., Inc. This is a solid resin having a specific gravity of1.14, a melting range of 212-248 F., and it is described and claimed inPatent No. 2,108,213 of February l5, 1938.

The Nuba resin is manufactured by the Neville Chemical Company. It is asolid dark stable resin differing in properties from the well knownCoumarone-indene resins, principally in that it is harder and tougher.We understand that it consists principally of cyclo-pentadiene and othercyclic dienes in highly polymerized state. It is manufactured and soldin three grades having the following characteristics:

We have also used Nevillite, a resin manufactured by the NevilleChemical Company, which has the following properties:

Specific gravity at 68 F 1.046 (average).

Color -Water white.

Form .Glassy lumps.

Melting points (graded) 50 F. to 329 F.

Iodine value .Approximately 2.

Chemically inert Strong acids, alkalies and salt solutions have littleor no eff ect and it is alcohol resistant.

In each instance we utilized a mixed solvent thinner comprising 80%, 150water-white kerosene, 10% hi-flash naphtha, and 10% pine oil. A smallquantity of ozocerite wax, or a small quantity of one of the metallicdriers, was in each instance included in the composition. We prefer touse, as an ingredient of the coating composition, a linseed cil whichhas been oxidized. We have found wholly satisfactory linseed oil whichhas been treated to a point at which it acquires a body as heavy asQ-tube by the Gardner & Holt viscosity tube test.

A preferred coating composition for our present purpose may be obtainedby Working up in a kettle equal proportions by volume of the thinner andthe total of other ingredients. To this mixture We add three times itsVolume of additional thinner.

We have succeeded in obtaining an iridescent effect, in which thetreated foil presents apparently all the tints of the spectrum byutilizing any one of the above-noted formulae in the manner hereinafterdescribed. We have also obtained a foil, treated in similar manne-r,which presents an iridescent effect, utilizing a coating compositionfrom which coumarone or its equivalents have been omitted.

It may be noted that such latter foil, having the coating film in whichcourmarone or its equivalents are not used, .possesses a less perfectadhesion between the metallic base and the film than a foil havingcournarone or its equivalents included in the coating compositionapplied to the metallic base to form the iridescent lm thereon. It isnot, however, either tacky or thermoplastic.

It has been explained that the speed at which the applicator roll, shownas the roll E of the exemplary apparatus, revolves determines therelative thickness of the coating which is applied to the foil. This ison the assumption that a composition of predetermined viscosity isapplied. It should be understood that the effect of the linear speed ofthe applicator roll surface is effective by relation to the speed oftravel of the foil. Thus utilizing a foil travel of 120 inches a minute,and a maximum furnace temperature of 600 F., while revolving theapplicator roll at 65 inches a minute, the foil developed a lightgolden, unvariegated color. By reducing the linear speed of theapplicator roll surface to 50 inches per minute, the other conditions ofthe process remaining identical, iridescence in the coated foil began tobe observable. With the other conditions identical, a full rainboweffect including apparently the entire spectrum was obtained when thelinear speed of the applicator roll was reduced inches or more perminute below the speed of 30 inches per minute.

It may thus be stated generally that, in order to obtain a definiteiridescence in the coated foil, the applicator roll should act at alinear speed substantially less than the linear speed at which the foiltravels.

It will be noted in the above that the speed of foil travel is feet perminute. Utilizing a zone of maximum furnace temperature 5 feet inlength, the foil is given a heat treatment 30 seconds in duration at themaximum furnace temperature of 600 F.

We have utilized a maximum furnace temperature as high as 820 F. toobtain our iridescent effect. At temperatures of from '735 F. to 820 F.we have found that the speed at which the foil passes through thefurnace should be so increased that the foil receives a treatment of nolonger than 20 seconds in the maximum temperature zone of the furnace.This is for the reason that an unduly extended heat treatment at suchhigh temperature serves to darken the foil, giving a color from brightpurple to a purplish black.

With increase in the speed of foil travel, the speed of the applicatorroll may also be increased, without thereby applying to the foil acoating so thick as to render it diiiicult to develop iridescence byheat treatment.

The coating as applied to the foil being adequately thin, and theduration of the heat treatment in the zone of maximum temperature beingslightly in excess of one minute, we have observed the development ofiridescence in the coated foil at a temperature as low as 550 F.

It is, of course, however, desirable for commercial reasons to utilizehigher temperature, and to pass the foil through the furnace at higherspeed.

We have not obtained the development of a full bright iridescence attemperatures substantially below 600 F., or substantially above 820 F.It is readily conceivable, however, that by establishing extremeconditions as to speed of foil travel, and by appropriately adjustingthe linear speed of the applicator roll relatively to the speed of foiltravel, the optimum effect might be obtained, both below and above thattemperature range.

The coating composition being suitable, and of appropriate predeterminedconsistency, the other factors which have been noted may be expressedroughly as the formula In this formula, A=the conditions producing anoptimum iridescent effect in the coated foil;

l bzthe maximum temperature to which the coated foil is subjected duringheat treatment; c=the speed of foil travel in given linear units; andd=the linear speed of the applicator roll in the same units. Inaccordance with this rough formular, and as otherwise explained above,as d approaches c, either b must be increased, or c decreased, to give agreater intensity of treatment. We have operated with a speed ratio of cto d as high as l5 to 2, and even as high as l5 to 1, to produce acoated foil in which the film is of light color, showing distinctiridescence.

It has been noted above, as a general factor, that a heat treatment toosevere, either in ternperature or duration, tends to the production inthe coating of a dark purplish coloration, deficient in iridescence. Inproducing our iridescent foil, it should be further noted as a generalfactor that increased thickness in the coating on the foil, irrespectiveof any other factor or factors, tends to the production of a darkereffect than the effect developed in a thinner coating.

While we are not certain as to the cause of iridescence in our compositefoil, we are led to believe that it is, in part at least, due to a lightdispersing thickness of the film on the metallic base; the effect beingrendered readily observable by the degree of opacity produced in thefilm by heat treatment of appropriate severity. Certain observationsbear out this theory. Thus, it has been noted that a film of unduethickness does not exhibit our desired light-dispersing effect. We alsohave noted that the film obtained when the applicator roll is run atexceedingly low speed to produce a lrn of minute thickness, fails toexhibit a readily observable iridescence. As the coating composition isspread on the metallic base, in preferred thickness, a very slightiridescence is with diiculty observable prior to subjection of the foilto heat treatment. It is in all cases to be assumed that the metallicbase to which the lm is applied does not function as a complete, orsubstantially complete, light absorbing medium;

Every example of our iridescent foil made with a coating compositioncomprising coumarone resin or its equivalents, exhibits, as heattreated, perfect adhesion between the metallic base and the lm, and thefilm itself is elastic, insoluble, is without thermoplasticity, and ishighly resistant to acids and alkalies.

At a temperature of 549 F. aluminum passes through a stage ofre-crystallization: Since aluminum is a metal to which coatings bondwith diiiiculty, it may be that, when aluminum foil is used as themetallic base of the foil, such fact contributes to the perfect bondbetween the base and the heat treated lm. In any event, it is a factthat, whether the base be of aluminum foil, or another foil, anapparently perfect, bonded adhesion between the metal and the lm isobtained.

Our iridescent foil is susceptible of many uses where ornamentalappearance is of importance. For example, it is useful in stage eiects,and for the purposes of general mural decoration and the like. It isalso highly desirable for use in wrapping confections, tobacco, andsimilar products, in which the attractiveness of the package possessesdenite commercial value; it is further desirable as applied as an outercovering to boxes, cartons, and the like. For all these purposes thefirm adhesion of the coating to the foil, and the fact that the coatingas heat converted is elastic, is resistant to solvents and the like, andis without tackiness at any temperature, gives the coating qualitiesgreatly enhancing its utility.

Because of the rm bonded adhesion between the non-metallic lm of thecomposite foil and the metallic base of the foil, and because of theelasticity of the film, the composite foil may be creased abruptly, andmay be flexed to follow complex contours, without cracking the film orperceptibly weakening the adhesion of the film to the metallic base.

While we have referred particularly to the application of the coating tometallic foils, such as aluminum foil, we have successfully applied itto other metals such as black iron, and to lightgauge sheets of aluminumand other metals which have not been worked down, or treated, to suchdegree that they exhibit the absolute deadness commonly associated withthe word foiL The above disclosure constitutes in part a continuation ofour copending application, Serial No. 24,702, led June 3, 1935.

We claim:

l. The improved method ,of coating metal which comprises ap-plyinguniformly to a metallic base an oleoresinous coating compositioncontaining a heat-curing resin in a thin iiowable state, drying thecoating on the metal by subjecting the same to moderate temperature,thereafter subjecting the coated metal to ai substantially highertemperature and regulating the thickness of the applied film, bycontrolling the amount of solvent thinner and the speed of application,and also adjusting the temperature and duration of the heat treatment soas to produce an optimum iridescent effectV in the coated foil,

2. The improved method of coating metal which comprises applyinguniformly to a metallic base an oleoresinous coating compositioncontaining, in a thin flowable state, a heat curing resin and asynthetic resin having substantially the properties of neutrality,adhesion and inertness to acids and alkalies possessed by coumaroneresin, said synthetic resin being selected from a group consisting ofcoumarone, polymers of dihydronaphthalene, and reduced hydrocarbonpolymers produced by the polymerization of petroleum distillatesobtained by vapor phase cracking, drying the coating on the metal bysubjecting the same to moderate temperature, thereafter subjecting thecoated metal to a substantially higher temperature and regulating thethickness of the applied film, by controlling the amount of solventthinner and the speed of application, and also adjusting the temperatureand duration of the heat treatment so as to produce an optimumiridescent effect in the coated foil.

3. The improved method of coating metal which comprises applyinguniformly to a metallic base an oleoresinous coating composition`containing a heat curing resin and coumarone in a thin iiowable state,drying the coatingyon the metal by subjecting the same to moderatetemperature, thereafter subjecting thel coated v'metal to asubstantially higher temperature and regulating the thickness of theapplied film, by controlling the amount of solvent thinner and the speedof application, and also adjusting the temperature and duration of theheat treatment so as to produce an optimum iridescent eifect in thecoated foil.

4. The improved method of coating metal in strip form while it is beingcontinuously 1 fed which comprises applying uniformly to a metallic basean oleoresinous coating composition containing a heat curing resin in athin flowable state, drying the coating on the metal by subjecting thesame to moderate temperature, thereafter subjecting the coated metal toa substantially higher temperature and regulating the thickness of theapplied film, by controlling the amount of solvent thinner substantiallywithin the range of seven parts of thinner by volume to one part of theother ingredients and by controlling the speed of application, and alsoadjusting the temperature and duration of the heat treatment so as toproduce an optimum iridescent eifect in the coated foil.

5. The improved method of coating metal while continuously feeding thesame, which comprises applying uniformly to a metallic base anoleoresinous coating composition containing a heat curing resin in athin flowable state, drying the coating on the metal by subjecting thesame to moderate temperature, thereafter subjecting the coated metal toa substantially higher temperature Within the approximate range of 600to 820 F. for a treating period of the order of one minute andregulating the thickness of the applied i'llm, by controlling the amountof solvent thinner and the speed of application, and also adjusting thetemperature and duration of the heat treatment so as to produce anoptimum iridescent elect in the coated foil.

6. The improved method of coating metal which comprises applyinguniformly to a metallic base an oleoresinous coating compositioncontaining a heat curing resin in a thin iiowable state, drying thecoating on the metal by subjecting the same to a moderate temperature,thereafter subjecting, the coated metal to a substantially highertemperature within the approximate range of 600 F. to 820 F. for atreating period of the order of one minute and regulating the thicknessof the applied film, by controlling the amount of solvent thinnersubstantially within the range of seven parts of thinner by volume toone part of the other ingredients and by controlling the speed ofapplication, and also adjusting the temperature and duration of the heattreatment so as to produce an optimum iridescent eiect in the coatedfoil.

7. The improved method of coating aluminum foil While it is beingcontinuously fed, which comprises applying uniformly to the foil anoleoresinous coating composition containing a heat curing resin in athin floWable state, drying the coating on the metal by subjecting thesame to moderate temperature, thereafter subjecting the coated metal toa substantially higher temperature and regulating the thickness of theapplied lm, by controlling the amount of solvent thinner and the speedof application, and also adjusting the temperature and duration of theheat treatment so as to produce an optimum iridescent effect in thecoated foil.

8. The improved method of coating aluminum foil While it is-beingcontinuously fed, which comprises applying uniformly to the foil anoleoresinous coating composition containing a heat curing resin in athin iiowable state, drying the coating on the metal by subjecting thesame to moderate temperature, thereafter subjecting the coated metal toa substantially higher temperature within the approximate range of 600F. to 820 F. for a treating period of the order of one minute andregulating the thickness of the applied film, by controlling the amountof solvent thinner and the speed of application, and also adjusting thetemperature and duration of the heat treatment so as to produce anoptimum iridescent effect in the coated foil.

9. The improved method of coating aluminum foil while it is beingcontinuously fed, which comprises applying uniformly to the foil anoleoresinous coating composition, in a thin flowable state, containing aheat curing resin and a synthetic resin having substantially theproperties of neutrality, adhesion and inertness to acids and alkaliespossessed by coumarone resin, said synthetic resin being selected from agroup consisting of coumarone, polymers of dihydronaphthalene, andreduced hydrocarbon polymers produced by the polymerizattion ofpetroleum distillates obtained by vapor phase cracking, drying thecoating on the metal by subjecting the same to moderate temperature,thereafter subjecting the coated metal to a substantially highertemperature Within the approximate range of 600 F. to 820 F. for atreating period of the order of one minute and regulating the thicknessof the applied lm, by controlling the amount of solvent thiner and thespeed of application, and also adjusting the temperature and duration ofthe heat treatment so as to produce an Optimum igidesggntdgffggt in thecoated foil.

10. As a neNarticle of manufacture, an iridescent foil comprising aflexible light-gauge metallic foil base and an iridescent-exhibitingfilm thereon, said iridescent foil being the product resulting from themethod defined in claim l.

11. As a new article of manufacture, an iridescent aluminum foilcomprising a flexible light-gauge metallic foil base of aluminum and aniridescent-exhibiting film thereon, said iridescent foil being theproduct resulting from the method dened in claim 2.

12. As a new article of manufacture, an iridescent aluminum foilcomprising a flexible light-gauge metallic foil base of aluminum and aniridescent-exhibiting film thereon, said iridescent foil being theproduct resulting from the method defined in claim 3.

13. As a new article of manufacture, an iridescent aluminum foilcomprising a flexible light-gauge metallic foil base of aluminum and aniridescent-exhibiting film thereon, said iridescent foil being theproduct resulting from the method dened in claim 9.

CLIFTON F. SCHMIDT, JR. GEORGE L. BALL.

